Many wireless communication systems assign transmission resources using a centralized scheduler. Typically, these resources have a time division multiple access (TDMA) component, wherein communications between a base station and a select mobile terminal are assigned to a given time slot. For downlink communications wherein a base station transmits data to a mobile terminal, the base station's downlink scheduler receives data intended to be transmitted to the mobile terminal, and allocates a certain time slot in which to transmit data to the mobile terminal. Notably, transmissions to different mobile terminals are assigned to different time slots to facilitate an ordered transmission of data amongst the mobile terminals being served by the base station. Similarly, in uplink communications wherein the mobile terminal is transmitting data to the base station for delivery across the network, the base station's uplink scheduler determines when the mobile terminal can transmit information to the base station, and via control signaling, instructs the mobile terminal of the time slots in which it can transmit data to the base station.
In many applications, the TDMA component of communications works in conjunction with other multiple access technologies, such as code division multiple access (CDMA), and the 3G high-speed wireless data systems, such as 1xEV and HSDPA. Those skilled in the art will recognize existing hybrid systems having a TDMA component, and will appreciate the applicability of the present invention to future technologies incorporating a TDMA component in a multiple access communication scheme.
In an effort to reduce interference caused by other mobile terminals, it is often desirable to control the transmission power of mobile terminals for uplink communications. In essence, the various mobile terminals should only transmit at power sufficient to achieve communications having a defined minimum of errors. Accordingly, various types of power control signaling are used to monitor error rates associated with communications for a mobile terminal and to control the mobile terminal's transmission power to achieve a desired error rate. Unfortunately, the movement of mobile terminals impacts uplink and downlink transmission channel conditions, and requires the base station and mobile terminal to cooperate in a manner to ensure that transmissions are properly received. As such, most systems have a built-in safety margin by using higher transmission powers for uplink communications. Unfortunately, this means that at any given time, these mobile terminals are transmitting at transmission powers much higher than necessary to achieve the desired error rates.
In similar fashion, the base stations often have to allocate excessive resources to ensure transmissions are properly received by mobile terminals during downlink communications. Although many base stations do not use power control schemes for transmission, they do often change modulation and coding techniques to make transmission more or less robust, as well as to transmit at higher or lower data rates. For example, the base station may attempt to modulate and encode data to maximize data rates, but must err on the conservative side to ensure that communications are properly maintained and error rates are less than a defined maximum value if channel conditions change. Again, significant safety margins erring on more robust modulation, more coding, and lower data rates unnecessarily impact the efficiency of the wireless communication system.
Accordingly, there is a need for a technique to enhance the efficiency of communications in wireless communication networks while minimizing interference in communications with other mobile terminals. There is a further need to more efficiently allocate resources in light of actual channel conditions to avoid the unnecessary safety margins built into existing systems.